This invention concerns a multi-layer cylindrical bearing.
Multi-layer cylindrical bearings used for wiper arms and carburetor bearings in automobiles normally have to withstand adverse conditions due to their outside installation. An example of this type of bearing, shown in the U.S. Pat. No. 2,691,814, is manufactured by sintering metal powder on carbon steel sheet so as to form a sintered layer, and then impregnating and curing a synthetic resin over the sintered layer to form a strip-shaped plate. This plate is then bent into a cylinder with the carbon steel on the outside forming a backing layer, and cut into desired length which are given a flange if necessary. Alternatively, the plate is cut into desired length before being bent into a cylinder. Finally, the outer surface is given an anti-rust plating of tin or zinc. This anti-rust plating is satisfactory as far as the surface of the backing layer is concerned.
There is still a small gap where the cylinder is joined, however, and the plating solution is not impregnated into the gap, so that this area is hardly plated. When the bearing is exposed to harsh conditions outdoors, therefore, rust starts to form at the joint of the backing layer. Rainwater causes this rust to spread to adjoining areas, finally preventing the bearing from functioning correctly.